Improvement in carbon-telephones



UNITED STATES PATENT OFFICE.

JOHN W. GILBERT, OF- PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO SAMUEL S. WHITE,

OF SAME PLAO E.

IMPROVEMENT IN CARBON-TELEPHONES.

Specification formingpart of Letters Patent No. 221,547, dated November 11, 1879; application filed September 24, 1879.

To all whom it may concern:

Be it known that 1, JOHN W. GILBERT, of Philadelphia, Pennsylvania, have invented a new and useful Improvement in Carbon Transmitters for Electric Speaking-Telephones, of which improvement the following is a specification.

My invention relates to that class of telephonic transmitters in which the air-waves impinge directly upon the carbon disk or button.

Its object is to increase the sensitiveness and'efficiency of such carbon disk by causing the sound-vibrations or air-waves to impinge upon or be deflected toward the center of the carbon, and to give greater elasticity to its central portion, which ends I attain by making the exterior side of the carbon disk, or that next the speaker, concave.

In the accompanying drawings, Figure 1 represents a central transverse sectionthrough a carbon transmitter embracing my improvement, and Fig. 2 a similar section through one of the carbons.

The parts of the instrument other than that above mentioned as constituting the subject matter of my invention being, some of them, well known, and others not being claimed by me as my sole invention, need not here be particularly described.

The base A of the case screws into a cap, 13,; provided with the usual mouth-piece. The carbon disks 0 0 (two only being shown, but a greater or less number may be used, as desired) are inclosed in a suitable insulating-envelope in the case. The connecting-wires pass from their binding-posts to their respective carbons.

By making the carbon disk comparatively thick at the edge itis better adapted to receive the envelopin gconnecting-wires and to resist crushing, while the thinner central portion responds more readily to the vibrations con-, centrated upon it.

It is obvious that the details of the instrument maybe greatly varied without departing from the principle of my invention.

The operation of the apparatus will readily be understood from the foregoing description.

'[ claim as of my own invention- The carbon disk constructed, as set forth, with a concave surface next the speaker.

In testimony whereof I have hereunto subscribed my name.

JOHN YV. GILBERT.

Witnesses:

ROBERT E. SMITH, THos. S. STOUT. 

